The present invention relates to electrically insulating static seals and in particular to a high voltage insulating seal with means to progressively expel air bubbles along the seal surfaces as the seal surfaces are compressed together.
In many apparatus such as the phase angle meter instrument disclosed in my copending application, Ser. No. 042,671 filed May 25, 1979, the interior of an enclosed housing is maintained at a potential substantially different than the potential exterior of the housing. It is therefore essential that the housing be electrically insulated to provide protection against damage and from electrical shock. A particularly serious problem arises if the housing has two or more parts which must be joined to form the housing enclosure or where enclosure access ports are required. Such junction must be adequately insulated to eliminate any conductive path between the inside and outside of the housing.
Previously, adequate electrical insulation has been achieved by disposing a rubber gasket between junction surfaces or by inserting a rubber plug in each access port. However, rubber breaks down where high voltages exist. This breakdown forms conductive carbon tracks along the interface of the gasket with the seal surface. In addition, it has been found that miniscule air bubbles, which exist along the seal surface, ionize and form conductive paths along the junction surfaces when high voltages are present.
Hence, the present electrically insulating seal assembly provides a configuration for the seal surfaces which captures and expels all air entrapments as the seal surfaces are compressed together and thus prevents formation of conductive pathways. The dielectric strength of the present seal is a function of the dielectric grease used and the length of the path along the gasket to seal surface interface from the interior to the exterior of the housing.